Smoothly turning off volume

i have music that im gonna put in the timeline…music& sfx…and i want is so that when someone clicks a button to another section, that the music on that particular section doesnt just cut off, that it goes from volume 100 to 0 smoothly, like if one were to turn the volume down on a radio. i just dont want it to cut off abrubtly

thanks in advance

somdow